Construction

In your group's Crystal Radio Kit you will find:

1- paper roll

1- spool of insulated wire

1- germanium diode

1- screw, washer, and nut

1- copper strip

5- push-pins

1- piece of sandpaper

1- cardboard square

Instructions

1. The first step in making the radio is winding the tuning coil. This is best done with two people. One person should hold the paper roll and the other the spool of wire. Poke a small hole about a 1/2" from each end of the paper roll. Take the end of the wire from the wire spool and thread it through the hole. Pull the wire through so that it is about a foot long. Put a narrow strip of transparent tape aound the end of the tube to keep the wire from slipping out during winding. Now, begin winding the coil. When winding the coil, do not overlap the turns, they should lie adjacent to each other. When you are close to reaching the second hole on the other side of the roll, unwind an additional foot of wire and cut it off near the spool. Thread the end of the wire through the hole as before and apply a strip of tape.

2. Attach the pre-drilled copper strip to the cardboard square using the provided screw, nut and washer.

3. Now mount your paper roll to the cardboard square using two pushpins through either end. Locate the paper roll so that the copper strip will gently rub across the top of the coil.

4. Add 3 more push-pins to the cardboard square as shown in the figure below. Connect the germanium diode beween the screw holding down the copper strip and one of the nearby pushpins. You'll make a better connection if you loop the ends of the diode around the screw and the pushpin. The side of the diode with the black band should point away from the copper strip.

   There is also a larger version available.

   

5. Loop the loose wires from the ends of the tuning coil a couple of times around each of the remaining pushpins.

6. Using the provided sand paper, gently remove the enamel insulation from the last inch or so of the wires coming from the tuning coil. Also gently sand (by rubbing in the same direction) the enamel wire along the path on the surface of the coil where the copper strip rubs.

7. All that is left now is to hook your radio up to an earphone, antenna, and grounding system (such as a cold water pipe) and you should hear music! By sliding the copper strip along the tuning coil, you should be able to hear several weak, but distinct, radio stations. For good electrical contact, you may need to press the copper strip firmly against the coil with your finger while listening to the radio.

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updated 3 Sept 1997

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